1. Field of the Invention
Exemplary aspects of the present invention relate to a fixing device and an image forming apparatus, and more particularly, to a fixing device for fixing an image on a recording medium and an image forming apparatus incorporating the fixing device.
2. Description of the Related Art
Related-art image forming apparatuses, such as copiers, facsimile machines, printers, or multifunction printers having at least one of copying, printing, scanning, and facsimile functions, typically form an image on a recording medium according to image data. Thus, for example, a charger uniformly charges a surface of a photoconductor; an optical writer emits a light beam onto the charged surface of the photoconductor to form an electrostatic latent image on the photoconductor according to the image data; a development device supplies toner to the electrostatic latent image formed on the photoconductor to render the electrostatic latent image visible as a toner image; the toner image is directly transferred from the photoconductor onto a recording medium or is indirectly transferred from the photoconductor onto a recording medium via an intermediate transfer belt; finally, a fixing device applies heat and pressure to the recording medium bearing the toner image to fix the toner image on the recording medium, thus forming the image on the recording medium.
Such fixing device may include a fixing roller heated by a heater and a pressing roller pressed against the fixing roller to form a fixing nip therebetween through which a recording medium bearing a toner image is conveyed. As the recording medium passes through the fixing nip, the fixing roller and the pressing roller apply heat and pressure to the recording medium, thus melting and fixing the toner image on the recording medium.
Since the toner image on the recording medium faces the fixing roller, as the recording medium bearing the toner image is discharged from the fixing nip, the recording medium may adhere to the fixing roller by an adhesive force of melted toner of the toner image on the recording medium. To address this problem, a separation pawl disposed downstream from the fixing nip in a recording medium conveyance direction may contact the fixing roller to separate the recording medium from the fixing roller and at the same time guide the recording medium to the outside of the fixing device.
However, since the separation pawl is in constant contact with the fixing roller, the separation pawl may produce abrasion marks on the fixing roller as its useful life is about to end. Accordingly, as a recording medium bearing a relatively large, solid toner image slides over the fixing roller, the abrasion marks on the fixing roller may scratch the solid toner image, producing gloss streaks or variation in gloss on the solid toner image.
To address this problem, the separation pawl may be isolated from the fixing roller while no recording medium is conveyed through the fixing nip. However, if a plurality of layered recording media is accidentally conveyed through the fixing nip or a recording medium is jammed at the fixing nip, the recording medium may enter between the separation pawl and the fixing roller and may be wound around the fixing roller.
On the other hand, the separation pawl may be sandwiched between separation pawl protectors that rotatably support a guide roller to prevent the separation pawl from scratching the toner image on the recording medium. For example, the guide roller projects farther than the separation pawl and the separation pawl protectors toward a conveyance path through which the recording medium is conveyed, thus contacting and guiding the recording medium conveyed through the conveyance path to the outside of the fixing device. Hence, the guide roller prevents the separation pawl from scratching the toner image on the recording medium, thus suppressing resultant gloss streaks.
However, if a rigid recording medium is conveyed through the conveyance path, the rigid recording medium may slide over the guide roller with increased friction therebetween. Additionally, immediately after the recording medium is discharged from the fixing nip, the toner image is not cooled and fixed on the recording medium sufficiently. Accordingly, the toner image may be scratched and damaged by the guide roller.